Non-linear resistive elements generally called a varistor show a characteristic of a resistance value thereof varying with a voltage applied thereto, i.e., have a non-linear voltage-current characteristic such that the element has a high resistance value showing an insulating characteristic when a normal voltage is applied thereto, while showing a low resistance value when an abnormal high voltage is applied thereto. Non-linear resistive elements having such characteristic are broadly utilized in a surge arrester or a surge absorber for the purpose of absorbing surge and noise, or in a voltage stabilizing element.
The non-linear resistive element is, for example, composed of ceramic sintered compact having zinc oxide (ZnO) as a primary component. The ceramic sintered compact is obtained by molding a powder including zinc oxide, at least one of a bismuth oxide, antimony oxide, and cobalt oxide as basic additive to develop a non-linear voltage-current characteristic, and various types of oxide added to further increase the performance, and by sintering the compact (green body).
The ceramic sintered compact is, for example, formed as a rectangular plate shape, circular shape, or in various shapes in accordance with the place it is mounted or the shape of a member which becomes the electrode (Patent Document 1 and Patent Document 2).